Short-base range-finder.



H'. D. TAYLOR. SHORT BASE RANGE FINDER.

APPLICATION FILED 111111. 11, 1911 "'7 SHEETEP-SHEETJ,

Patented J an. 2, I912.

HEB s E! E1 gig E l??- fl w dfli ww H. 1). TAYLOR.

SHORT BASE RANGE FINDER.

APPLICATION FILED MAR.11,.1911.

1,013,849. Patented Jan. 2, 1912.

7 SHEETS--SHEBT 2A Fly. 9.

EB 9V H. TAYLOR. SHORT BASE RANGE FINDER.

APPLICATION FILED MAR. 11, 191] Patented Jan. 2, 1912.

7 SHEETS-SHEET 3.

H.D.TAYLOR.

SHORT BASE RANGE FINDER. APPLICATION FILED M'AR.11, 1911.

1,01 3,849 Patented Jam 2, 1912.

7 SHEETS-SHEET 4.

H. TAYLOR. IISHORTBASE RANGE FINDER.

1 APP'LIOATIQN FILED MAR.11,-1911.

Patented Jan. 2, 1912.

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H. D. TAYLOR. I SHORT BASE RANGE FINDER. 7 APPLICATION FILED MAR. 11, 1911.

- 'Patnted Jan. 2, 1912;

7 SHEETS-SHEET 6.

W E'GEEE v H. 1). TAYLOR;

. SHORT BASERANGE FINDER.

APPLICATION IILED'MLR. 11, 1911.

7 SHEETSSHEET 7.

Patented Jam, 1912.

.with the right eye is to lar ely HAROLD DENNIS TAYLOR, OF IBISHOPHILL, YORK, ENGLAND.

SHORT-BASE RANGE-FINDER.

Specification of Letters Patent.

- Patented Jan. 2, 1912.

Application filed March 11, 1911, Serial No. 613,821.

To all whom it may concern: v

Be it known that I, HAROLD DENNIS TAY- Lon, subject of the King of Great Britain,

rcsidingat Bishophill, York, in the county of York, in the Kingdom of England, have invented certain new and useful Improvements in Short-Base Range-Finders, of which the following is a specification.

This invention relates to short-base range-finders, and it is the principal object of the invention to provide a range-finder combining the advantages of binocular and stereoscopic vision.-

The advantages obtainable are as follows 1st. The .gain in illumination to be obtained. It is well known that the physiological eifect of superimposing the image seen with the left eyeupon the image seen increase, if not to double the apparent rlghtness 0f the object viewed, assuming that the two constituent images are of equal brightness.

2nd. The greater sense of relief or solidity which is yielded when both eyes are used. This is the case even independently of any genuine stereoscopic effect, as can be proved by taking two exactly similar photo raphs printed from the same negative an combining them into one picture in a stereo-' scope. It will then be found that a much greater sense of reality and relief is obtained.

3rd. The further sense of perspective relief and solidity following from the two views as seen by the right and left eyes respectively being views as seen by the right and ,left ends of the instruments res ecti vely, whereby a genuine stereoscopic e ect is obtained.

The distance between the two human eyes is about gth of a foot and yet the eyes can realize a certain amount of stereoscopic relief upon objects at least 200 yards away, or at a distance 3000 times the separation between the eyes. finder has a base length of 12 ft., or has its two windows through which the distant object is viewed 12 ft. fapart, then a genuine stereoscopic effect may be expected on objects as far oil as 12 ft.x3000 or 12,000 yards,

supposing the right hand'view is brought panying drawin s, in which,

Similarly, if a range.

which ,my invention is most easily applied is that described by me in my Britis patent specification No. 7322 of 1907 and having only one object glass, one half of which receives light from ;an optical square at one end of the instrument and the other half light from an optical square at the other end of the instrument.

The invention is illustrated in the accom- Figure 1 is a iagram illustrating in plan the essential features of an instrument of the knowntype above referred to, but mom tied to suit binocular vision. F1g..2 shows in vertical section the separating or halving prism combined with one achromatic lens of the erecting eyepiece. Fi 3 is a diagram'of the pupilary imageso the ob jective as formed by, the halving prism.

Figs. 4 and 4 are two views, elevation and 3 plan respectivel showing ajtotally reflecting right-angle prism as used in the apparatus. Figs. 5 and 5 are two views showm the images of a flag staff as seen by the 1e and right eyes respectively in the instrument. Fig. 6 shows the su erposed images as seen by both eyes simu taneously when directing the vision. on to the lower half. Fig. 7 shows in section a form of halving prism, the converse of that shown in Fig. 2.-

Fig. 8 is a diagram showing the case of the .instrument in plan. Fig. 9 illustrates the graduating board for graduating the instrument, Fig. 10 shows the casin of the instrument in front elevation. ig. 11 shows the box (t') at the left hand end of the tube of the instrument, as seen from beneath with the bottom late or cover removed. Fig. 12 shows t 0 box (.F) at the right hand end of the instrument, as seen from above with the top cover removed. Fig. 13 is a detail view on a smaller'scale showing the mechanism for actuating the swinging prism in the box (t .)"Fig. 12. Fig. 14 1s a sectional plan view of the tube of the instrument in the center part thereof.

Fig. 15 shows across section at A-A, Fig.-

14. Figs. 16 to 19 are detail views hereinafte'r referred to. Fig. 20 is a plan,and Fig. 21, a front view showing diagrammatically a modified arrangement for an instrument 0 d are supposed to be absent,--1t is instrument are screened oil by means of two qgaque p lat es; of metal, while,- the overlap- --parallel edges of the two metal plates, and

sfiirliBgitiSh:hpeeifieeticijj there wasifslmwnr 'kthusiall gthe light from the primaryrignages an optical square at zl tto reflept thr 4.1 i: Mi.

..a .f n- We, z .u toward the eyeplece, which optical square half images'of the ment there weretwdfoiitside the objective iand 'tivaatthemw four altogether both cases. i yen numberfis necessary .to' the; correctoriiihtiition" of the ima e, and I ticablelf Atf is the to prism an' at "p is the rangereadiiigachromatieprism, which swings abbut an parallel to itsjfrefractmg? edger; being tuated' .f by"? means of a. es eem? we.

a matine the ia-saute subba atfthe 'd stant :aobjech' ted on" the scale .i offrangesg "lien" "two-"im'ages shownan i-TEsichhzil'iifthe' object glass 0 (u er 1 "'lhese mages are refined JjectE as} VlewQd t By fi the left hand optical h uperiifiposed upon the samQ'distaiit object" as viewed ig hand .op'tical square 9 ot the separating or halviiig pris'in figwhich is cemented (see the four-lens erecting eyeiece. ,This-lens,

if the h'aiyinij rism' were not there, would he'ri In "Fig. 3, the "i'rcles r",'1- repreigfht 1 View or image as. ll. hand end of the/juit from hard rl of the 'strumentf" The knit-lying achied range scale, as I he about? o'incicling with the. ciri p w simi r-1y represeht, the let v ew seen from "the-i-left:

which passes throu h the two overlapping o ect glass is allowed to three reflections 'from' the-"upper halves/of the reflectors m" m?'.'andm That is the op'phsit-to the upper half of the objective,

ceiyes light fronis? atthe right hand end'of the instrur'nent, which light "travels along '8, arid thence; after three [reflections ofi' the lowerhallfof the obiectiye. "'"I" I have already hown that eachhalf of "over the h'alvln'g rism h the pencils fornifracted upward and collected 'again the which fallsb etweeri'thewalls of the-slot and is passed, :while the imaige from-zthe bottom -.half of the objective and right hand end .of' the instrument also thrown on the lower forming the leftview Z1 1 After'erectidfi' by the' second or er'ector lens a this lightforms the image in the distant 'rpbj'ect as seen *b ythe left hand optieal e iiare of the instrument; as 'shown' 1n Fi above .thelhalyingi line! Similarly Min -the ower= half: of the ofview the eye see; 'onlythe unniixed -*im;ige of the distonr half i'of thef objective and passing is'theright hand yiew-, as seen through the riglihhanjd optical square ssj Th s right V ew is als'oshown 1n fig! 5 beiovx the -halw ping halves 'r" and!" of'the two images of iathmebjecti-wes; fall into the vgap between the' pass on. through secondor ereetor lens the left hahd end. of the lnstrumentfafter whileffthe lower half "of the objective ret'he 'objecti yeithrows an i a ebnm "anii all upper half of'thefield of view,.-so that the eye sees therein-a pure unmixedimageof the optical squares. is upsidflowfiand placed the lower half'of the tube,; then underneath half ofthe-halyingprism, is refracted still theobjectitte andjeft endv oi the instrument, I

ing line. The left and right images are, therefore, divided from one another by the sharp lineof demarcation yielded'by the ridge of the halving prism and any parallax subtended by the base at the distant object shows-itself as a horizontal separation or break as shown in Fig. 5,--i.mtil-the swinging prism 1 which neutralizes and measures the parallax, is operated so as to neutralize the said parallax and so bring the twoimages into coincidence, when the range of the/object is indicated on a suitable scale.

Let it now be supposed that the light from the upper hall of the objective which falls upon the upper half of the halving prism and the light from the lower half of the objective which falls upon the lower half of the halving prism and which is afterward refracted to form respectively the two semi-circular pupilary images of the objec tive l and 1"", is, instead of being screened oil and wasted, reflected off at right angles and thus diverted into the left eye of the observer. Then it is evident that if Fig. 5 is the view as seen by the right eye, wherein the up er in'iage is the view seen by means-of thele t end of the instrumentand the lower image is the view seen by means of the right end of the instrument, then Fig. 5 will represent what is simultaneously presented to the view of the left eye, wherein the upper half of the field is the view seen by means of the right end and the lower half of'the field is the view seen by means .of the left end of the instrument. Ilence while the upper image appears say 10 seconds to the right of the lower image as viewed'by the right eye, on the other hand as viewed by the left eye the contrary isthe case and the upper appears 10 seconds to the left of the lower image.- If then the two eyes are respectively directed upon the lower images so as to cause the two lower images to merge into one, as in the usual act of binocular vision, then it is quite clear that simultaneously two images of the upper image will be seen equally at either side of the lower image, as in Fig. 6, and thus the effect of the parallax as seen by one eye only will be doubled for the two eyes conjointly. Now the lower half of the field is stereoscopic in the true sense, for the right eye gets the view from the right end of. the instrument and the left eye the view from-the left end, but in the upper half of the field the contrary holds good; the right eye gets the view from the left end and the lefteye the view from the right end. Hence in the upper half of the field the views are complementary but not truly stereoscopic. Nevertheless. the effect is more real andsolid looking than, and prmrtically twice as luminous as, a monocular view. In the lower half the stereoscopic relicfis fully realized. Now the effeet when taking the range,- am of a distant ship, is that if the eyes are concentrated part of the lower field, then it stands out with a bold sense of relief, while just above the halving line, the same mast orspar appears more orless doubled (see the flagstafi', Fig. 6) as though nearer to or farther off from the observer than the same spar just below the halving line. But on operating the swinging prism 72? which brings the images into coincidence, the apparent doubling of the upper image decreases until the two images merge into one, and then the mast just above the halving line seems to range itself at the same distance from the observer as the mast just below the halving line, and seenrs to correctly join on to the. same. While for single eye vision -the effeet of operating the swinging prism is tocause one image to approach. and. line up with the other fromone'side only; in the case of binocular vision the "effect is that there are'seen to be two images inthe upper half of the field whichapproach andlineup with thelower image from both-sides simultaneously. Or else it is leq'uallyfeasible, though not so good in effect, fGl'.tb.B two eyes to merge the two upper images into one, while the lower images will then apear doubled, when the latter will merge into one and line up with the upper image when the swinging ris'm is operated to produce coincidence. my way, so long as there is any part of the parallax unneutralized. it

tilinear slot or gap right 'through it for the free passage of the light forming the two, centrally overlapping semi-circular pupilary in'iages l and .11, which latter light is then reflected off the ordinary right-angled prism 11' through the right erector lens 0' into the right eyepiece Z), a; while the to and bottom parts of the first right-angle prism d relic-ct the other moiety of light 2. e.-the

outlying semi-circles l and 1' through the left erector lens 0 into the left eyepiece b a". The erected. image thus formed in front of the left eyepiece is received upon another sort of halving prism, one form of which shown in vertical section in Fig. 7', so

lot)

shown in Figs. Fl: and 4, and to cut a rec- 7 that the image of the first halving prism ridge (h, Fig. 2) falls correctly upon the junction line of the two prisms It, In, Fig. 7. The object of this isto cause the two separated sen'ii-circular pupilary images r and l of the half objective to fall together again outside the eyepiece so that they shall sir-tultaneously fallinto thep'upil of the eye, in-

- separated. I

.. I. will. now give I instructions for-enabling "any expert inthe construction ofloptical and.

scientific instruments. :to ina-kel ai binocular range-finder I in" accordance with my- .inven'! tion; will: presumethatv object-glass is of 51} inches aperture and that the base length is 12 feetw-It thus" constitutes an instrument of great-light gathering power. 15 The two .-inagnifyingmpowers of eyepieces employed are abOut-QQHa-ndAO'dian eterS, the .fern erfor 'usezwhenstheilightior definition: is POOIa, The instrument-.2 consists of'yan' inner built-up; steel :tube (:F'igsg 8, 14, .15, etc/5).; 0t llifsdiameterlancl.12.to116 wire ga ge, carrying -the.=.tyv0 :bOXQS Fund. it fixed to :its ends and lying-iconcentrically within a still-larger steel tube g. 1 The inner, tube andi boxes areueonnected to" the outer tube 1-2.5 by: means ot 'ttvo pairs ofu-ta'perd pivots y,

Figs. 112 and 12, at-each-end.;-;IThis. arrangen1'ent L very "largely. shields the? inner tube carryingthe boxes from vertical buckling when .the- .sun shines hotlyl uponcthe top of 530 theoutentubeu Such vertical-buckling will cause halving: error- 01; inequality in height of the two images from; the'tw o ends of the instrument. The. .ai-r;jspacewbetvteen" the tubes is a great .proteetion.-.. against..thisend- ..35 moreover the .innertube nwmgsteits pivot connections cannotrbe "buclel'edi vertically by any vertical strain falling uponytheIouter tube In -order tonstil-l. .;further reduce any ;,p-os sible halving ;.erizors;s itfiisfiadvisahle to 1' :40 cover the 'inne tulienuith. flannel. and then push-"on oven that;-zandinotictooi' tightly, a copper. stnbe{(notnSliown) gmade of about 1/3'2nd.-ineh sheet coppexnt This may be'in ethree lengths for :convenience.

, the lupperlhalfaoirthe object-.g ass. The

'-plan,."h;ig'.= 11; shows, this box upside down,

-for conyehi ene', asthe solid. fioor to which mthe parts are liited-zis-reallylat .the top whilethe lid is atithe-bottorinw Thus the optical h an downward ":so'z. that; the 'bQhlZOlTl edges of-its twoani'rrors area-on a.,level with the center. ofgthe' objectgzlass os l mfl m .mi, ar'e threensilvered circular, 1plane.- and parralleliifilass nnrrors whose centers are about level-with the center of the obj ective. -:'1'hese f three mirrors, as well as those.ofwthez-optiealgsquaites, are preferably made the-n1i1ni1er-decribed in the specificationpf Britishlatent. No. 13562- .of .plane parallel glass). has .to traverse this The outer 5 tube carries flanged-bearing rings u Figs.

ofi 1907' The achromatic prism p forv setting-the zero, lies OPPQSitQdthQgfUPPCI'.1131f of the objective,;so;that-the ligl tp-irom the :rii'st-a'ntobject entering thewindow lprism' .betore it reaches. the optical square 8'. After reflection .froinrthemptlcal square 1t isi reflected successively -,,f r,omthe upper *llitl-yelsiof the three mirrors m-',. m 1113, and .tl-ieneeinto.theupper half of the objective 0. ell-The box, V

instrument 'hou n in Fig. 12 asseen from above ecntujinsan optical square fixed to the; floor of the box, and ate .lower;;level or opposite to thwlmverhalf-of the objec .tiveo. Q 2 h I: 9 is the; swinging achromatic prism' 'whose angular position, when the images .arecoincident,- indicates .the range. This prism is preferably a duplicate ci y/except that it shouldZbeJJargeuj-It-is shown. as arranged between the, windoww. and op.- tieal square s instead of lying. in the path oft-he light. from the squares along the :tubeas in Fig. 1. H 1 'Ihelight from the distant object enters the box I! through the win(lo\ v U52 and travzerses the-swinging prism and then, after being doubly'refleetedoll the optical square s fpasses alunghnd parallel to the interior of "the .innertube I. underneath .the'optieal square 5-. and is then reflected successively from the-lowerhalves of the tl'l-reemirrcn's 112/, m m. and thence into the lower half of. the objeetiveor Thus the upper half of the objective receives light from the left hand end and the lower half of the same from the'right ham] end oli the instrument.

' At a distance behind the shjer-tive 0, equal to the fooatlength is the halving prism 71 shown in plan in Figs. 1 and 14-. and in sec tion-in Fig.2. Each of the two planeslopes of this prism are at an angle equal to i sisa Where'A is the clear aperture and I" is the- .75 it the right handend ofthe {focal length of the objective and 'n is the refractive. index of the halving prisin. This halving prism is cemented by its plane side to the plano concave flint lens. a of the acl'u-oniatic first lens (c, f.) of the 4-lens eyepiece (or halving lens-sec Fig. 2) whose ofliceyit .to throw aniimage (reiulereil overlapping and double by the halv ng prism) of the objective into the left hand reflecting prism cl shown in l igs. l, 4, 5H, 1 4 and-16. Tl1 ese t\v0 overlapping images of the objective are as it were pupils or common sections of all the pencils of rays divterglng. from points in the inniges Fol distant ibjects; projec ed by the ohject'n e onthe upper and lower slopes of the halvnn; prism. 1 a The left hand prism is so slotted.

"through (Figs. 4 and 16) as to allow the overlapping images of the half objective r thence to the right eyepiece, but the solid upper and lower portions of the left hand prism (Z reflect the uppermost and lowermost images of the half objective into the left eyepiece. Since the distance between different pairs of eyes varies considerably, an adjustment is provided for one of the eye pieces. For this purpose the left hand prism d is mounted in the manner shown in Figs. 14, '15 and '16. The left eyepiece 31 is affixedto a metal slide 24, Figs. 14 15, capableof about inch of motion to right and left of a. mean position, operated by a small milled head with a suitable rack and pinion gear. This slide 24 embraces between two jaws the ball or disk termination 26 (Fig. 1a) of a lever 27 attachedto a frame 36 which is pivoted at 28 and carries a short arm \vlth a downwardly projecting pin in its end. This pin fits into a slot in a second lever 30 just below it, .which is part of a frame carrying the slotted prism (Z which frame is pivoted at 35 so that the lever 30 is just double the length of lever 29. This arrangement secures that when theleft eyepiece traversed 'through an angle of say] 2 degrees as subtended at 28 then the prism rotates through half the said angle or 1 degree, and thus the light is always reflected straight toward. the left eyepiece. The first lever frame 36 also carries the left erector lens 0 The prism itself is fixed by means of fine ground Portland cement into a nickel. iron tray with a retaining groove around its inner edges, corresponding to a similar retaining groove in the prism (see Fig. 16). The tray is pivoted underneath the center of the reflecting side and is capable of being tilted and thus leveled. by means of three pairs of antagonist screws and of being rotated slightly in a horizontal plane by means of other an-- tagonist screws. The right hand prism d is similarly mounted in another nickel iron tray with similar adjustments, carried by a shelf forming part of the casting, while a prolongation of thesanie casting carries the right hand ercctor lens (2.

Both erector lenses are capable of longitud'inail adjustment by screwing the cells carrying them to and fro in the flanges which hold them. This is for the purpose of getting the two images thrown into the left hand .and right hand eyepieces to the same scale of magnification. 'l'he flanges carrying the two cells also should be provided with a slight adjustment upward and downward as well as atdtmg adjustment by means of three pairs of antagonist screws,for-squaring them on with respectv to the eyep'lfe cesa The eyepieces themselves or rather the eye lenses thereof (a, b, and a", 5 Fig. 1) are mounted upon two swivels pivoted at 33 and 34' each swivel carrying .a, high and alow power eye lens of powers .20 and 40 respectively.

The left swivel '33 is pivoted upon the before-mentioned metal slide 24 for adjusting the distance between the two eyepieces in use. 1

Each swivel carries, as part of itself, two tubes within which the actual eye-lens tubes slidcto and fro. These latter tubes are provided with three pins projecting through three straight slots parallel to the axis and cut in the pipes, into three spiral slots cut in and through an external sleeve or tube capable of rotation. Hence if the latter is rotated, then the eye-lens tubes and their lenses move in and out for focal accommodation and afiange on the external focusing sleeve should be provided with a scale of diopters engraved on it, from 0 for normal long sight down to -5 diopters for short sight a+2 diopters for long sight. The two eyepieces 31 and 32 can then always be set to the same focus or sight to suit any given observer.

The-field lenses for both-high and low powers are fixed immovably in the tube or casting carrying the eyepieces; but the left hand field lens is constructed in two parts so as to do duty for the halving prism Iii h", before described and shown in Fig. 7. This construction is shown in Figs. 17 and 18in vertical section. and elevation. Each half is the thicker half of a lob-sided lens like that shown in Fig. 19, both sur-' faces being spherical. The formula for the excess of thickness of one side of each lens over the other is where E is the required difference of thickness, D is the diameter of the lens, n isthc refractive index of the glass, F is the effective distance from the center of the left erector lens to the back or eye-side of the left field lens, and C is'the estimated distance from the center of the left erector lens 0 (Fig. 14) to the center of eitherof the two semi-circles of light as'projected from the center point of the halving lens or prism h (Figs. 2 and 14) through the outlines of r and Z (Fig. 16) on to the said erector lens. After two wedging lenses have thus been mizdc and turned circular with their edges square to their first surfaces which. face the ercctor-lens, then each is cut in half, the thinner halves being rejected and the two thicker halves 40, after careful trimming down to exact scmi-cicles with t-heputedges forming about, i

face facing the erector lens, are then placed in their cell as shown: in Fig.- 17. It is es-' sential that the diametral edges which come together on the eye side should be exceedingly sharp. and free from minute chips, and also that a closebut not quite perfect contact should take place between them in the eye-side,' although there may bela larger and quite perceptible gap. on the side facing;the erector lens. For this reason a nar row strip of very fine black tissue paper should separate the edges on the eyeside,

Whichprevents an actual contact, which would inevitably lead to a chipping ofthe edges. v

The right hand field lens'isathinner lens of nearly the same: curves butof the usual simple form. The lefthand erectedf image is formed exactly upon the horizontal junc tion of the t'wowed'ged half lensesftOon the eye side, but the right. hand erector image is formed in the air about atent-h} of-an-inch behind the side next tothe eye,

but both images are supposed to be at the same actual level with respect to the tube of the instrumentand the eye lenses. In

Figs. 14 and 15 is shown an indiat rubbe r forehead rest and eyeshade 39 In Fig. 14 is shown thearrangementfor actuating the halving adjustment of the Lin- V strument, whereby the images from the, right end and left endof the instrument are adjusted to exactly the same height in the field of view. There is a',knurled-head at 42 whi'ch turns a grooved pulley .41 car-Q rying ,athin copper wire endless cord 44,

whose other end goes over'a grooved wheel 43' placed under the left. opticalsquare 3- shown in Fig. 11; this wheel 43 forms part of a right-hand screw of 401threads per inch screwing into the-floor of the box, and has threaded into its center a smaller caliber male right-handed screw of threads per inch whoseupper end is fixed to the optical square frame 8 in such manner that it (the screw) cannotirotate; Thus one turn of the wheel 43 will only raise orlower the optical square frame by 1 I The: optical 1 square frame I shown) keep 46 up in contact-with 455 I A The leveling of the optical squares is of great importance. 1 First the righthand box square 5 fixed up in it; is set u'p'l'and leveled upon a leveled planetplate and a couple of leveled pencil'or ink'inarks oi-crosses are i viewed, as "reflected oi "the optical square, l

by means of a urvj eyqr tele o e-1W1'or theodolite and the ptiea1squareis tilted by means of 'it sj three attachment screws; until the, reflected ima es of the twodeveled marks appeardevehwith'one an After the whole inst/fitment isjput together the left hand opticalfsquare i's leveled level and directed uponitwo'bl'ack" straight lines. e p atlyr ra 1e1i i er a and at a: distance apart EQI'IQII' i theft base length and at the ame distance" from the instrument as the scaleofranges used for graduating; Then, as seenin the right hand eye-piece; the. upperj'lialf of; one of these black lines should f ppje'ar exactly in, alin'e ment with the lowergh'alf of the'same lin'el Both above and below the halving line the black line should'appear as'all one straight vertical line. "'Ifi'tdjoes not there is a bend or elbow at the halving line, it isproof that the left hand optical square not level or upright like theright hand ey and the orb e ld b "si ht l qi iii 'i h. wo female straw 'plilss n ttf iailvin wheel 4:3,"Figl 11.1 "lhej iinage iiijtheleft han y p e s ould;i btbeadj tifo equal magnification: uprightness'" until after the right; hand eyepiece is'correct; I With' regardjto the, three mirrors 'm}'., as, mi, of course all jthree should beset. pet? pendicular to their frame whiclif should be provided with cheeks forming surfaces, for

squaring them from. 'After the "tr nsienttached to -the floor of the boxiithel whole frame will want a little adjustment in, order v to. secure, that: the optical .a xis'ffot the tele;

scope. is, reflected off so, as v to strike aj point t on the furthermost, mirror of the riglitlhand optical square that is central 7 (in plan) on such mirror "and level withlt'lie'. axispf'the tubes; For this, vpurpose 12 finch laperture i p ei n et i it hsl yqent-fa y nitheg r ptj fifths iss i land a small" blackspot on aisniall, piece of Pap r sum d (9 1 t9 the ri 3 wf t 'i an: mit rifc th r ht 111mm i ii j l squa ef h t s' fifiet 'axi; sqen-sh ild S r t-{ L enth am re s d i'l ed by i s thr 1fi ii d ivnal th 1 m as ot th said, spit it oi jtli'eii 'erl 'f th e d ei vi cffl g:

Ls igh djus men s 7 [i i sewn exis s in a imuth t stdi ltm. s'l etji te d a i m y l ad. t the ai lnminaidapf bout 1. fet f ell-lsn tht it's cial key inserted through a specially shaped.

aperture whereby any risk of the adjust ment being played with IS obviated. A copper wire endless cord 49 is stretched over this pulley, whose other end passes over the I pulley l8 fixed to the end of t 1e screw 50 for adjusting the zero prism p, which is shown in Fig. 11. When the instrument has been sighted upon a convenient test object at a known distance or infinite distance and the range drum has been set exactly to that range, then if the two images as seen in the right hand eyepiece are not exactly c0inci-- dent in the horizontal direction, they can be made so by operating thepulley 18 by means of the proper key. This-swings the prism 32 around slightly. about its vertical bearings at its left hand end. a r

The mechanism for actuating the swing ing prism p and translating its movements into ranges is shown in its essentials in Figs. 12 and 13. The frame of the prism. 12 swings about an axis 7, and a toothed sector 15 is fixed to the. underside of the frame of the prism 22? engaging into a pinion 16 fixed (zen trally on a stem 2 just above a worm wheel 3 thereon. The radii of the sector and the pinion are preferably arranged so that one complete rotation of the worm wheel and I pinion will cause the swinging prism to swing-through-an angle ,of not less than 82 degrees, that is from the position of minimum deviation up to the position where the extra deviation will neutralize the parallax of an object 2000- yards away, which will generally be the minimum range the instrument is required to register. The worm wheel 3 should have ninety-six teeth engaging into a worm 17 having a double thread, so that forty-eight turns of the worm 17 will correspond to one turn of the worm wheel. The worm wheel is rotated by means of the rod or steel tube 1 which is actuated from the elevation handle as shown on a small scale in Fig. 10, and also in Fig. 13..

At the bottom of the elevation handle a: is a preferably 1 to 12, so that since the shaft 1 rangesfrom infinity down to 2000 yards. A spiral hollow groove cut in the surface of the drum is utilized for driving a reading mark up or down so as to follow the track of the spiral.

Fig. 9 shows roughly the form of graduating board a that must be used. The two vertical black lines at the ends are supposed to be exactly the base length apart when the Vernier mark his set to infinity, and this sameye'i'niei' mark can be traversed by somebody at the board along the scale of marks whose distances ((1) in inches from the infinity mark are given by the simple formula I)B It wherein D is the distance of the range-fin her from the graduating board (in inches), B is the base length in yards and R is the range (in yards) to which the required mark is to correspond. For D a'convenient distance is 100 yards or 3600 inches and two collimator lenses of' about 51' inches apertures and 100 yards focal length must be provided for fix- .ing opposite to the two windows of the in.

strument, at a distance between their centers equal to the base length. Thus as the vernier mark is traversed along the scale of ranges the right handmark is carried nearer to the left hand or fixed mark, and as the tion, after which the two images are brought to coincidence by operating the zero prism p,-Fig. 11, at the left hand end 'of the instrument. Then the graduating board operator sets the board to 20,000 yds. and the rangefinder operator turns the n'iill'ed haul 8, Figs. 10 and 13, until the two images are brought exactly into coincidenceowing to the swinging of the range prisnrfrom its position of minimum deviatirm. lVlien coinand so on until all the ranges have been gone through. After this there will be found a series of marks upon the range drum forming a spiral curve and the next procedure consists in properly engraving and number-' drums can. then be copiedfrom the first one,

provided the base length and angles of; the

swinging prism are kept constant.

. The two right angled-prisms shown 20 and 21 in Figs. 14 and 15 are for the purpose of. reflecting the light from the finder objective 22 into the right hand eyepiece and for this. purposethey are mounted on a swivel so that after the object has been found -aLnd-gotintothe middle of the field as seen by' bothright and left hand eyepiece, then the prisms-are swung. outof the way and then 'the right eye sees the rangefinder view.

At 18, Fig. 14, is shown an astigmatizer len'swhich is placed eighteeninches tothe left .oftheyhalving prism. -It consists of twoplane-concavecylindrical lenses to in. radius, the axesf of the cylinders being horizontal. Each lens must have one edge (the'j'unctionedge) trimmed straight and parallel tot-he axis-of the cylindricalsur-v face and at a distance of .37 inch from the thinnest part of the lens; Then the two lenses are put together. up to their junctionedges on a temporary piece of plate glass and the whole trimmed to the required circular size (2.7 5 diameter) in the lathe, after whichthe two semi-circular lenses can be placed in their proper cell. This lens is thrown "in and out ofpperation by .means of turning the winged nut 23, Fig, .14, which, by'means'of the rod connection 19 throws over the. lever attached to the cell of the astlgmatizer.

The optical squares and.their frames are preferably constructed inlaccordance with by British .patent specifications Nos. 13562/ 1907, 20315/1908 and7392/1910, and the mirrors m, m m are likewise held (prefi erably) between' ball screws and pallets as described in the last mentioned specification. I-will now give dimensions,radii of curvature's, thicknesses and positions forall the optical parts of the instrument, in inches, as well asfspecifications of the glasses reqiiireda j- 1 a I Rig7it ha'ncl optical is'quare. (s-.)'

if "l vf 'hetd fr' q qr f-Y I .e olniilrrors 5.75;;625rd5t5 1c I l;

rtor m; size 5.8O'd1am. circular x annery r5 size 5.80 3 Ml size the most gtransparent; silicate or borosilicate :crown: gl s as well as heme. pa l l p ane ;.wi.ndows; 11: m, ,which are respectively of;

angles.

I The angle between thelsurfaces of the. crown, prism is l 4:2 .505 and that off the sodium line z) I,

Borosilicate crown having. 125:1.5118 and p s ep ve iC emfififi- T I Ordinary'densc flint :havingv l. 61 7.andf dispersive -power =3. 6..6 -f. The finishedsiz; two' ange prisms is 6.95by 3.6 by .eQgcentral thickness. 'lzT-he finished size of thegtwo ,ZGI'Q l prisms.,isf5 5 O by 2.75 byAO central thicknesslf The objective ,0 is oi tiicl' n eterand 16 inches. focal length -,and to the following radii of curvature. .In every easel shall, give the radii vof"thejsujrfaces intherorder' in which the ligl t',;passes.through {them} r.= +17-.5 1,=:+1s.75.- -m= 48.7514: 465.

e"e e.

w on ein t eei e ivei xi 9.

' The crow-n lens is of silicate crown, hay-.-

i'ng'n,5:';1-.518'anddisp::p0wer:60.2: .1; 'The flint 'len's i's of 'Schotts flint type 01266 having n :L'545 and di'sprpow er:43.93. If 5 a The halving prism halving-lens is 2.05 diameter and tl e radii' of the latterz' -i 1 The crown lens 1810f: ordinary crown having n :l;516'and disp; power: 58.7;..- z

The concave flint lens: is of. .S'chotts: flint type 0.1266 havingen .:l 6054c and dispi p0wer::43.93'. I i.

The angle :oiislope. or;,each--, side of: the halving prism is 2 ;18aw' I :v a l The left hand 'erector lens; isa'triple. com bination: I n: +4125, rg= +7.5; 1;; -7.5; r.= -1.'5, 1t= 51.05, T6: #353;

The first i1 m,1e iborosilicate crown having n 1. 51 65 and disp, power; 641.2. c 1;,- "L; I. The flint lens isof. Schottsf'.type',0.1266 having'4z 1.60 54. and disp., power:d3.93,

The 3rd crown.lens is ofordinary ,crown havingn 1.5.l7 3 and. disp. power- 60.3. The central thicknesses, are V respectively about.20, .10 andJ/LOinch The glasses are,,siniil. arrespectively to those "u e $9 the we er'es ter' l The c th leffi.P m??? aw .1; :T he left hand double' vedged fieldlensfis diameter "I /l0 and each thick.

"1-|=+2.4s,a +.5o,e= i5o,a: +17291-0 w Qentral thieknessesof lenses are .24fand v .08., Finished diameters fio.

crown lenses are of light crown glass I having n IJlST and (lisp. powerz6 t9. a 'llhe flint lenses are of light flint having"- ;.n-D;; 1.5f( tand (lisp. power:41.6."

,Tl1ehigl1 ipower eye. lenses are to. the

n= H5075, 1-2= +.445, a: -.445, n-=' +1.79. 2O

wished diameters are .625. I

The cro'wn lenses are of silicate crown ravin"gn :1 .5l7 and disp. power:58.2. Elie flintlenses; are of dense flint having 1 0115 162 and disp. power 362. The two prisms (Z and a?" (FigSu13 and 14) for re f 'flectingihe l'lglltg llltO the. eyepiece" are of 'fany transparent horosilicate crown glass. Thelefthand-prism d should be of the following dimensions; Total height:1.75, angle of freflecting surface .45". lVidth parallel to main tube: 1..04. Breadth across main tube at front: -1 .60. r

- The right 'ha nd'prism a should be about 1.05 high. The slot cut through the left hand prism for the passage of the light to the other prisn should be .385 to .390 high at theorificefacing the halving lens, tapering. 11ip'-to-".42 about 1 inch farther baclcf The nearest distance. between left "erelctor lens-and' its field. lens should be 1 about? .8 in. and that between righterector lensand its ficldlensiabout9.0.inches.

Thereflecting hypotenuses should be sil- -1vred,-as-it is a fact that total reflection "never takes placeuinless thesurfaces are 1 1 'kept scrupulously i While good veringwvill reflect (by internal reflection) as niuclras 98%per cent. andlthat without the trouble of frequent cleaning, a somewhat dirty nakedsurface will only reflect internally about 92tper cent. of the light; I will now describe in rough outline in connection with Figs. 20 to 23 a method of applying my invention to a rangefinder "having two objectives. .In the first place it does not appear possible to retainthe two objectives inyone straight line. so the line of so one telescope lnust be behind but parallel to theother; The two objectives are shown at :ihand 6Lwhi'le 52.21nd'62 are the two halving-prisms'and lenses. The images formed a by the objectives and reflected into them by the two optical squares (not shown) fall 3 Central thiclcnessesare .24; and .06. Fin

1240' in; across thefitransmitting surfaces by upon the halving,prisnis,whichlatter cause a the right halvingprism 62 goes through the upper image of the objective over; the optical square 63 and is reflected ofl t e optical square 64. into the left eyepiece vs 1616. it is thrown by the erector .lens 65 into the upper half of the field of view.

The light from the upper half of the right halving prism 62 goes through the lower 7 image of the objective and is reflected OK I the optical square 63 into the righteyepiebe Y where it is thrown by the erector lens 66 'into the lower half of the field of view. The

light from the lower half of the left halving prism 52 goes through-the upper image of.

they objective over the top of the optical square 53 is reflected by 54 into the right eyepiece where it is thrown by the erector 9O lens 55 into the upper half of the field of view. The light from the upper half of the left halving prism 52 goes through the lower image of the objective and is reflected off the optical square 53 into the left eyepiece where it is thrown by the erector lens 56 into the lower half of the field of view. Hence the two lower fields are truly stereoscopic and the two upper fields supplementaryas inv the previously described instrument.-

The four erector lenses must be. of such focal lengths and so placed as to give equal magnifications so, that the whole apparatus requires very careful designing, and then the resulting instrument will not be so good as that previously described. The erector lens56 will have to be semicircular, for all four erector lenses must have their centers level with the centers of the objectives. The erected images thrown by the erector lenses must be received upon the back edges of double wedged field lenses like that I have described and illustrated in Figs. 17 to 19. This is in order to retract the two Lpupilary images of the object glass into one and the same central position just behind the eye lenses,,.57 and 67 I declare that whatI claim is 1. The short base rangefinder, a pair of binocular eyepieces, means for producing in the upper and lower halves of oneeyepiece views of the upper and lower parts of a distant object as seen from the right and. left hand ends of the instrumel'lt, and for producing in the upper and lower halves of the second eyepiece views of the-same parts of the object asseen from left. and right ends respectively of the instrument, where by if there is any unneutralized parallax it will show itself as a displacement of the upper image to the right of the lower image for the one eye and to' the left of the lower image for the other eye, and whereby also the apparent separation or parallax is made to appea doubled when both'eyes are binocularl focused upon either upper or .lower images, in combination with means including a scale whereby any parallax can be removed and whereby the amount of adjustment required to remove the parallax can be read on thescale.

2. In a short'base rangefinder, the combination of a pair. of binocular eyepieces, means for producing in the lower half of the left and right eyepieces views of the bottom parts of a distant object as seen from the left and right ends respectively of the instrument, means for producing in the top halves ofthe left and right eyepieces views 'of the upper parts of the distant object as seen from the right and left ends of the instrument respectively, means for adjusting the 'positionof the images in such a manner as 'to remove the parallax, and means for indicating the adjustment required.

3. In a short base rangefinder the combination of a pair of binocular eyepieces, means for receiving and transmitting views of the upper and lower parts of a distant object as seen from both the right and left ends of the-instrument, means for partially superposing the pupilary images of the objective formed by light coming from opp'osite ends of the instrument, means for transmitting the images such that the two eyepieces receive in the lower parts thereof images from the right and left ends respectively of the instrument, and in the upper parts thereof images from the left and right ends respectively of the instrument, together with means for adjusting the position of the images as seen in the instrument whereby any unneutralized parallax can be removed, and means for indicating the adjustment required in order to remove the said parallax.

4. In a short base rangefinder, a pair of binocular eyepieces, means for receiving and transmitting views of a distant object as seen from opposite ends of the instrument, the said means including a swinging prism, mechanism for moving the same about an axis parallel to its refracting edge andv for indicating the amount of movement on a scale, in combination with means for splitting up and separating the upper and lower partial images of a distant object as viewed from o posite ends of the instrument and means or combining into each eyepiece the upper portion of the image from one end of the instrument and the lower portion 1"" the images being respectively from the left and right ends of the instrument in the one and from the right and left ends of the instrument in the other of the eyepieces.

5. In a short base rangefinder the combination of a pair of binocular eyepieces, means for receiving and transmitting images of a distant object as viewed from opposite ends of the instrument, said means including adjusting mechanism whereby the image as seen from one end can be caused to move for the purpose of eliminating any parallax, an object glass through one half of which the image fromone end of the instrument passes and through the other half of. which the image from the other end of the instrument passes, and means for splitting up and transmitting separately into the two eyepieces the upper andlower halves of the images as seen from opposite ends of the instrument. 4

6. In a short base rangefinder, the combination of means for receiving and transmitting images of a distant object as seen from opposite ends of the instrument, and for adjusting one of the images in such manner as to eliminate any parallax in the images as viewed, a slotted reflecting member and means for transmitting and erecting upper and lower half images of the object received thereon into the-upper and lower halves of one of the eyepieces, and a second reflecting member adapted to receive the remaining half. images which .pass'through the slot of the said slotted reflecting 'member together with means for transmitting and erecting the latter half images into the corresponding halves of the other eyepiece.

7. In ashort base rangefinder, the combination of means for receiving and transmitting images of a distant object as seen from opposite ends of the instrument, and for adjusting one of the images in such a manner as to eliminate any parallax in the images as viewed, means for transmitting and erect-' 'ing the upper half image from one end of the instrument and the lower half image from the other end of the instrument into the one eyepiece, separate means for transmitting and erecting the lower half image from the first end of the instrument and the upper half'image from the second end of the instrument into the second eyepiece, and means for adjusting one of the eyepieces and the transmitting apparatus connected therewith simultaneously in' the required ratios for the purpose of adjusting the separation of'the eyepieces.

8. In a short base rangefinder, the combi- I nation of means for receiving and transmit 1'25 ting images of a distant object as seen from opposite ends of the instrument, and for adusting one of the images in such a manner the image'from the other end of the instru-1' t5 ment, the said upper and lower portions of I viewed, a reflecting surface and m as to eliminate any parallax in the images as cans for transmitting and erecting upper and lower half images from opposite ends of the instrument into one of the eyepieces, a second reflecting surface and meansfor transmitting lower and upper half images from corresponding opposite ends of the instrument into the other eyepiece, and means for adjusting the position of one of the eyepieces relatively to the other, adapted simultaneously to adjust, with half the amount of angular movement, the one of the reflecting members associated with the said moving eyepiece.

9.,In a short base rangefincler, the combination of means for receiving and transmitting, images of a distant object as seen from,- opposlte ends of the instrument, and for adj usting one of the images in such a manner as to eliminate any parallax 1n the images as viewed, means for splitting up the upper 4 and lower half images from the two ends of v the instrument and directing them sepa-" rately into the two eyepieces, a doubly-refleeting pair of prisms, an eccentrically placed finder objective, and means .for swinging the said pair of prisms whereby the image from the said finder objective may be diverted when required into one of the eyepieces. r a 10. Ina short base rangefinder, the 0.0m-

bination with means for receiving and transmitting images as seen from OPPOSI'IZB' ends of the instrument of means for diverting the pupilary images of the objective formed by light from. opposite ends of the instrument into two partially overlapping separate images, a slotted reflecting member for transmitting the upper and lower slngle portions of the pupilary images and a sec my. name this 28th .day of February 1911, in the presence of two subscribing witnesses."

HAROLD DENNIS TAYLOR. VVit-nesses:

L. E. BUOKLEY, CHARLES E. TAYLOR. 

